http://developer.yahoo.com/performance/rules.html
- Minimize HTTP Requests
- Images : CSS Sprites are the preferred method for reducing the number of image requests. Combine your background images into a single image and use the CSS background-image and background-position properties to display the desired image segment.
- Use a Content Delivery Network
- Add an Expires or a Cache-Control Header
- Gzip Components
- Put Stylesheets at the Top
- Put Scripts at the Bottom : The problem caused by scripts is that they block parallel downloads.
- Make JavaScript and CSS External: Using external files in the real world generally produces faster pages because the JavaScript and CSS files are cached by the browser.
- Split Components Across Domains : The HTTP/1.1 specification suggests that browsers download no more than two components in parallel per hostname. If you serve your images from multiple hostnames, you can get more than two downloads to occur in parallel.
- Reduce DNS Lookups : DNS lookups take time. Reducing the number of unique hostnames has the potential to reduce the amount of parallel downloading that takes place in the page. Avoiding DNS lookups cuts response times, but reducing parallel downloads may increase response times.
- Minify JavaScript and CSS
- Remove Duplicate Scripts : Due to large number of developers and size of project its possible a script etc may get loaded multiple times.
- Don’t Scale Images in HTML
- Avoid Empty Image src
- Use Profiling tools to identify which parts of your code are consuming more time and more memory
- Fetch Data in Parallel : (multi curl for PHP, node.js, etc)
- Use EXPLAIN statement to analyze your SQL queries. Based on that add proper indexes
- Prepared statements in SQL need to be parsed just once
- Use Opcode Cache which will save the server from parsing your php again
- Use Memcache DB for storing frequent calls to the database
- Use MySQL Master Slave for faster read access
- See if schema needs to be split vertically or horizontally for faster access